A large variety of machines are known for the manufacture of mesh bags from tubular mesh for the packaging of a wide range of fruit and vegetable products, such as citrus fruit and root vegetables.
One particular type of machines for the continuous manufacture of mesh bags are those which comprise feeding devices for the tubular mesh and a first and second band or sheet of heat sealable material, in addition to a means of opening the tubular mesh consisting of an expansion core, situated in a vertical floating position inside the tubular mesh, supported by at least one pair of rotating rollers outside the mesh, the axes of which are solidly joined to the machine.
In addition to the elements described above, these machines also comprise one or several traction devices, generally consisting of pairs of rollers that that rotate in opposite directions, between which the tubular mesh and the bands are forced to circulate simultaneously and together in a descending direction along the outside of the expansion core. Other common components of this type of machines are welding devices, which are responsible for welding the bands of heat sealable material to predetermined sections of the tubular mesh as it passes over the aforementioned expansion core, and devices for cutting the tubular mesh and closing the lower end of the cut section, thus forming the bottom of the bag.
The bands or sheets of heat sealable material of the resulting mesh bags are used to join the lower ends of the bag and form the bottom thereof, and to then join the upper ends of the bag after the filling thereof, thus closing it at the top. At the same time, the bands are used to print the bag's identifying information, its contents or for advertising purposes.
In the type of bags described above, problems usually occur when the storage capacity of the tubular mesh between the bottom and the mouth of the bag is not sufficient for the length of the bands that join the bottom with the mouth of said bags. For example, it can happen that as the bag is being manufactured the capacity of the tubular mesh that is pulled out is excessive for the length of the bands that are pulled out together with the mesh, the result of which are bags in which the product contained in the tubular mesh hangs out of one or both sides of the heat sealable material bands. On the other hand, when the capacity of the tubular mesh that is pulled out is not sufficient for the length of the bands that are pulled out together with the mesh, there will be a surplus space between the heat sealable material bands and the tubular mesh that contains the product, whereas the ideal situation is that the band does not lose too much contact with the tubular mesh.
It therefore becomes apparent that there is a need for a device that enables the relationship between the length of the band or bands of a heat sealable material and the storage capacity of the tubular mesh that is pulled out simultaneously and together with the bands to be regulated in order to achieve bags that, once filled with the product, maintain an optimum relationship between the storage capacity of said tubular mesh and the length of the band or bands that join the mouth with the bottom of the bags.